Allows you to access the subfields in the virtual tape system parameter set by the Pre-ACS Installation Exit. The parameter is defined as a 256-byte character string including one or more sets of 2-byte length field followed by the value. The use of &MSPARM(n), where n is the field number, indicates that indexing is requested. If &MSPARM is specified without indexing, then the default is to access the first field of the parameter (for example, &MSPARM1) result by default).

 &MSPARM          first field of the parameter (default)
 &MSPARM(1)       first field of the parameter
 &MSPARM(4)       fourth field of the parameter